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LARGE-EDDY SIMULATION OF AN OSCILLATING-ROTATING TURBULENT FLOW

Stefano Salon
Dipartimento di Oceanografia e di Geofisica Ambientale, Istituto Nazionale di Oceanografia e di Geofisica Sperimentale-OGS B.go Grotta Gigante 42/c, 34010 Sgonico, Trieste, ITALY

Alessandro Crise
Dipartimento di Oceanografia e di Geofisica Ambientale, Istituto Nazionale di Oceanografia e di Geofisica Sperimentale-OGS B.go Grotta Gigante 42/c, 34010 Sgonico, Trieste, ITALY

Vincenzo Armenio
Dipartimento di Ingegneria Civile Universita degli Studi di Trieste 34127 Trieste, Italy; Dipartimento di Ingegneria Civile e Ambientale, Universitá di Trieste, Piazzale Europa 1, 34127 Trieste, Italy

Abstract

In the present paper the effect of rotation over a turbulent Stokes boundary layer is investigated using large-eddy simulation. Both the vertical and the horizontal components of the rotation vector are considered in the equations governing the flow: this is a key point in the developing of Ekman boundary layers.
The main consequence of rotation is the breaking of the symmetry between the two half periods that characterizes the purely oscillating boundary layer. In agreement with relevant literature, this produces a stabilizing/destabilizing action over the turbulence activity. Turbulence appears enhanced compared to the purely oscillating case, especially during the second half cycle. Non-zero values of all Reynolds shear stresses in conjunction with the generation of a mean shear in the cross stream direction give rise to a larger production of turbulent kinetic energy. As a consequence, rotation increases the thickness of the turbulent boundary layer when compared to the case of the equivalent Stokes boundary layer. Finally, remarkable three-dimensionality is observed in the turbulent field.